The invention relates to a labelling station for articles, more particularly bottles, having a number of stations disposed one after the other along a path, namely a gluing roller, a label box, a label-transferring cylinder and at least one label-removing element which is rotatably mounted on a rotating support and is moved past the stations with each rotation of the support and which has an outwardly curved label-receiving surface rolling on the front label of the label box and on the other stations respectively, the drive provided for each label-removing element being a cam drive comprising a fixed double cam disc, common to all the removal elements, with single-side cams disposed spaced-out in two planes one above the other and two sets of engagement members which are mounted via a support element on a driving shaft of the removal element and with the rotation of the support ensure by positive connection with the two cams the constrained movement of each removal element over its full rotation, the driving shaft terminating in front of the plane in which the first cam closest to said shaft lies, while the engagement members associated with the second cam are mounted rotatably offset on a bridge member lying between the two cams and borne by the engagement members of the first cam.
Labelling stations of the kind specified are known and have proved their value in practice. They enable high throughputs to be achieved, since the removal elements perform exclusively rotary movements and no oscillating movements, so that the positive and negative accelerations which are required to roll the removal elements by their curved receiving surfaces at the different stations can be relatively small. In the prior art labelling stations the rotary movement of the removal elements is derived from outside curves with which engagement members engage and transmitted via transmission gearing to the removal elements. The engagement members can both be disposed symmetrically and have operative lever arms of the same length (DE 38 11 869 A1) or be disposed asymmetrically and have lever arms of different lengths (DE 39 08 378 A1). In the latter case the rotationally offset engagement members of different lengths allow improved constrained guiding at critical places. In any case, such drives, which require transmission gearing, are expensive and due to the large number of structural elements participating in the rotary movement they are imprecise and not exactly quiet and low-wear.
In another prior art labelling station (DE 29 01 853 C2) the cams of the double cam disc of the cam transmission of each removal element are internally toothed after the fashion of a lantern gear toothing. In this cam transmission associated with each cam disc are four engagement members disposed on a common support non-rotatably located on the removal element driving shaft, which extends as far as a bearing below the underside engagement members. The advantage of such a cam drive is that transmission gearing is no longer required. However, the number of engagement members is substantially higher than their number in the other prior art labelling station, since otherwise in view of the relatively low teeth secure engagement cannot be ensured over an angle of rotation of 360xc2x0 of the removal element. For this reason, even with the two cams in each phase of the rotary movement at least three engagement members are engaged, namely two adjacent engagement members of one set and one engagement member of the other set, while in the phase of the transfer of the principal guide, even four engagement members are engaged, namely two members of the first set and two members of the other set.
It is an object of the invention to provide a labelling station of the kind specified wherein the drive of the removal element is as quiet and low-wear as possible with low construction expense.
This problem is solved according to the invention by the features that at least in the zone of the stations the double cam disc with its two cams is so constructed after the fashion of an internally toothed lantern gear that the rotary movement of the removal elements is derived directly (without transmission gearing) therefrom, while at the same time except for short transitional zones of the engagement members only one engagement member per set is in engagement with the double cam.
The labelling station according to the invention ensures a secure engagement over the full range of rotational angle of 360xc2x0 of the removal elements using a minimum of engagement members, since due to the bridge member the teeth of the lantern gear toothing can extend into the zone of the imaginary elongation of the driving shaft. Except for short transitional zones, two active engagement members are enough for such a secure engagement of the engagement members and therefore also for the initiation of a torque. This applies even in the particularly critical zones in which the downward rolling movement requires a high torque, as in the starting phases of the rolling movement at the different stations. As a whole, therefore, minimum constructional expenditure is involved. Reduction of noise and wear are achieved by the elimination of the transmission gearing and the engagement of the engagement members, reduced to a minimum. To reduce the acceleration movements, the modulus can even be so designed that it produces a slight backward rotation at the end of the movement between the stations.
In critical zones, in which the rolling movement requires a high torque, in one embodiment of the invention this is provided for by the feature that of the engagement members only one engagement member has the longer operative lever arm than the other engagement members and in the initial phase of the rolling movement of the receiving surfaces on the stations said engagement member is additionally in torque-operative, driving engagement with the double cam.
In a possible feature of the invention, to further reduce noise while still providing secure guidance, at least in certain zones the lantern gear toothing is constructed with clearance at the bases of the teeth and/or in the zone of the stations the engagement of the engagement members is limited to the tooth flanks of the cam.
According to another feature of the invention the modulus of the double cam between the stations is so large that after leaving a station the removal element is rotated only as far as the required rotary position at the start of the rolling movement on the next station. Preferably the modulus between individual stations is adapted to rotary movement up to stoppage. This can be achieved if when a station is left behind the rotary movement is continued at only a slightly reduced rotationally angular speed up to an angle at which the rotary movement is resumed at the next station. In this way even stoppage may occur, in which the drive emits no further noise.
The modulus of the lantern gear toothing in the zones between the stations can be varied in value. On the one hand to enable articles to be conveyed along the label-transferring cylinder, but on the other hand to make the stations as accessible as possible, which must be kept free for the frequent intervention of the operating personnel, the value of the modulus between the label-transferring cylinder and the gluing roller can be as large as possible; in the extreme case, as described, it can even be to the stoppage of the rotary movements, while in the zone of the gluing roller and the label box it is very small, so that these two stations can be disposed at an angle of approximately 90xc2x0.
Advantageously, to allow an optimum design of the lantern gear toothing the mutual rotary angle offsetting of at least some of the engagement members is xe2x89xa090xc2x0. To reduce wear and noise, also advantageously the engagement members run gently on to and off the supporting tooth flanks by the drawing-back thereof.
To obtain an embodiment which is particularly effective in the reduction of noise and wear according to the invention in the direction of rotation of the support the internally toothed cams have in a portion both downstream of the label box and also downstream of the gripper cylinder a substantially larger modulus than in the zone between the gluing roller and the label box, and the engagement member with the longer operative lever arm is at the start of the cam portion with the larger modulus in torque-operative engagement with a flank of a tooth of the associated cam, which has in the zone of the tooth tip a maximum angle of 70xc2x0 in relation to the radius of the support through the axis of rotation of the removal element. The angle of inclination should be 50xc2x0 at most, the optimum value being approximately 60xc2x0, the result being particularly favourable conditions for the introduction of the engagement member with the larger lever arm.
The introduction conditions can be further improved by the feature that immediately after leaving the label box, the particular removal element is accelerated until the engagement member with the longer lever arm comes into engagement with the associated cam.
Lastly, advantageously for optimum conditions of engagement and introduction of the engagement members according to the invention at all stations the tooth tips of the double cam lie laterally of the radii of the support extending through the centre of the stations.
Advantageously the invention can be put into effect with a central lubricating system for the bearings of the driving shaft and the engagement members. In that case according to the invention the driving shaft of each removal element has a bearing which is disposed above the support element for the engagement members and above which a lubricant supply element is disposed fixed on the support. The bearing is lubricated when it passes the fixed lubricant supplying system. The lubricant drips by gravity from bearing on to the engagement members. Lubricant distribution is particularly effective if on its side adjacent the bearing, the support element takes the form of a distributing plate for the lubricant dripping from the bearing and to be delivered to the engagement members partially extending beyond the edge of the distributing plate.